In order to change the control rods and fuel elements in a nuclear reactor a device is known having a pair of side-by-side grabs, one adapted to fit and lock onto the top of the fuel element and the other adapted to lock onto the top of a group of control rods. This arrangement allows the adjustment of a reactor by remote control in that this double grab is mounted on the end of a traditional arm operated by remote control with various servo motors.
The principal disadvantage of such a device is that it is extremely expensive. A separate set of controls, actuators, motors, sensors and the like is necessary for each of the grabs; thus the expense if elevated. In addition, such a device is relatively bulky and has a limited service life due to its extreme complexity.